1. Field of the Invention
This invention relates to a plasma display panel that is capable of improving the brightness as well as preventing a mis-discharge. Also, the present invention is directed to apparatus and method of driving the plasma display panel.
2. Description of the Related Art
Generally, a plasma display panel(PDP) radiates a fluorescent body by an ultraviolet with a wavelength of 147 nm generated during a discharge of He+Xe or Ne+Xe gas to thereby display a picture including characters and graphics. Such a PDP is easy to be made into a thin film and large-dimension type. Moreover, the PDP provides a very improved picture quality owing to a recent technical development. The PDP is largely classified into a direct current(DC) driving system and an alternating current(AC) driving system.
The PDP with an AC driving system is expected to be preferred for future display devices because it has advantages in the use of a low voltage drive and a prolonged life in comparison to the PDP of a DC driving system. Also, the PDP of an alternating current driving system allows an alternating voltage signal to be applied between electrodes having dielectric layers therebetween to generate a discharge every half-period of the signal, thereby displaying a picture. Since such an AC driving system for a PDP uses a dielectric material, the surface of the dielectric material is charged with electricity. The AC-type PDP allows a memory effect to be produced by a wall charge accumulated on the dielectric material due to the discharge.
Referring to FIG. 1 and FIG. 2, the AC-type PDP includes a front substrate 1 provided with a plurality of sustaining electrodes 10, and a rear substrate 2 provided with a plurality of address electrodes 4. The front substrate 1 and the rear substrate 2 are spaced in parallel and have a plurality of barrier ribs 3 therebetween. A mixture gas such as Nexe2x80x94Xe or Hexe2x80x94Xe, etc. is injected into a discharge space defined by the front substrate 1 and the rear substrate 2 and the barrier ribs 3. Each sustaining electrode 10 consists of a transparent electrode 6 and a metal electrode 7. The transparent electrode 6 is usually made from Indiumxe2x80x94Tinxe2x80x94Oxide and has an electrode width of about 300 xcexcm. Usually, the metal electrode 7 has a three-layer structure of Crxe2x80x94Cuxe2x80x94Cr and has an electrode width of about 50 to 100 xcexcm. This metal electrode 7 plays a role to increase a resistance of the transparent electrode to a high resistance to thereby reduce a voltage drop. Such a sustaining electrode 10 makes a pair within a single plasma discharge channel. Any one of the pair of sustaining electrode 10 is used as a scanning/sustaining electrode that responds to a scanning pulse applied in an address interval to cause an opposite discharge along with an address electrode 4 while responding to a sustaining pulse applied in a sustaining interval to cause a surface discharge with the adjacent sustaining electrodes 10. Also, the sustaining electrode 10 adjacent to the sustaining electrode 10 used as the scanning/sustaining electrode is used as a common sustaining electrode to which a sustaining pulse is applied commonly. A distance a, between the sustaining electrodes 10 making a pair is set to be approximately 100 xcexcm. On the front substrate 1 provided with the sustaining electrodes 10, a dielectric layer 8 and a protective layer 9 are disposed. The dielectric layer 8 is responsible for limiting a plasma discharge current as well as accumulating a wall charge during the discharge. The protective film 9 prevents damage of the dielectric layer 8 caused by a sputtering generated during the plasma discharge and improves an emission efficiency of secondary electrons. This protective film is usually made from MgO. Barrier ribs 3 for dividing the discharge space are extended perpendicularly at the rear substrate 2, and the address electrode 4 is formed between the barrier ribs 3. On the surfaces of the barrier ribs 3 and the address electrodes 4, a fluorescent layer 5 excited by a vacuum ultraviolet ray to generate a visible light is provided.
As shown in FIG. 3, the PDP 20 has mxn discharge pixel cells 11 arranged in a matrix pattern. At each of the discharge pixel cells 11, scanning/sustaining electrode lines Y1 to Ym, hereinafter referred to as xe2x80x9cY electrode linesxe2x80x9d, and common sustaining electrode lines Z1 to Zm, hereinafter referred to as xe2x80x9cZ electrode linesxe2x80x9d, and address electrode lines X1 to Xn, hereinafter referred to as the xe2x80x9cX electrode linesxe2x80x9d are crossed with respect to each other. The Y electrode lines Y1 to Ym and the Z electrode lines Z1 to Zm consist of the sustaining electrode 10 making a pair. The X electrode lines X1 to Xn consist of the address electrodes 4.
FIG. 3 is a schematic view of a PDP driver shown in FIG. 1. In FIG. 3, the PDP driver includes a scanning/sustaining driver 22 for driving the Y electrode lines Y1 to Ym, a common sustaining driver 24 for driving the Z electrode lines Z1 to Zm, and first and second address drivers 26A and 26B for driving the X electrode lines X1 to Xn. The scanning/sustaining driver 22 is connected to the Y electrode lines Y1 to Ym to thereby select a scanning line and cause a sustaining discharge at the selected scanning line. The common sustaining driver 24 is commonly connected to the Z electrode lines Z1 to Zm to apply sustaining pulses with the same waveform to all the Z electrode lines Z1 to Zm, thereby causing the sustaining discharge. The first address driver 26A supplies odd-numbered X electrode lines X1, X3, . . . , Xnxe2x88x923, Xnxe2x88x921 with video data, whereas the second address driver 26B supplies even-numbered X electrode lines X2, X4, . . . , Xnxe2x88x922, Xn with video data.
In such a PDP, one frame consists of a number of sub-fields so as to realize gray levels by a combination of the sub-fields. For instance, when it is intended to realize 256 gray levels, one frame interval is time-divided into 8 sub-fields. Further, each of the 8 sub-fields is again divided into a reset interval, an address interval and a sustaining interval. The entire field is initialized in the reset interval. The discharge pixel cells 11 to data are selected by the address discharge in the address interval. The selected discharge pixel cells 11 sustain the discharge in the sustaining interval. The sustaining interval is lengthened by an interval corresponding to 2nn depending on a weighting value of each sub-field. In other words, the sustaining interval involved in each of first to eighth sub-fields increases at a ratio of 20, 21, 23, 24, 25, 26 and 27. To this end, the number of sustaining pulses generated in the sustaining interval also increases into 20, 21, 23, 24, 25, 26 and 27 depending on the sub-fields. The brightness and the chrominance of a displayed image are determined in accordance with a combination of the sub-fields.
FIG. 4 shows signals applied so as to drive the AC-type PDP. In FIG. 4, the AC-type PDP is driven with a drive cycle being divided into a reset interval for initializing the entire field, an address interval for selecting the discharge pixel cells 11 displaying data, and a sustaining interval for sustaining a discharge of the selected discharge pixel cells 11. Reset pulses RPx and RPz are applied to the X electrode lines X1 to Xn and the Z electrode lines Z1 to Zm in the reset interval. A reset discharge is generated between all the X electrode lines X1 to Xn and all the Z electrode lines Z1 to Zm within the PDP 20 by the reset pulses RPx and RPx to thereby initialize the entire field. In the address interval, a writing pulse WP including data for one line is applied to the X electrode lines X1 to Xn and scanning pulses xe2x88x92SCP1, xe2x88x92SCP2, . . . , xe2x88x92SCPm synchronized with the writing pulse WP are sequentially applied to the Y electrode lines Y1 to Ym. Then, an address discharge is generated between the X electrode lines X1 to Xn and the Y electrode lines Y1 to Ym by voltage differences between the writing pulse WP and the scanning pulses xe2x88x92SCP1, xe2x88x92SCP2, . . . , xe2x88x92SCPm. By this address discharge, the discharge pixel cells 11 displaying data are selected. At this time, a wall charge and charged particles are formed at the discharge pixel cells 11 generating the address discharge, whereas a wall charge and charged particles are not formed at the discharge pixel cells 11 without data. In this address interval, a positive DC voltage lower than a voltage level of the writing pulse WP is applied to the Z electrode lines Z1 to Zm to prevent mis-discharge between the X electrode lines X1 to Xn and the Z electrode lines Z1 to Zm and between the Y electrode lines Y1 to Ym and the Z electrode lines Z1 to Zm. In the sustaining interval, a sustaining pulse SUSP having an inverted phase with respect to each other is applied to the Y electrode lines Y1 to Ym and the Z electrode lines Z1 to Zm. At this time, a sustaining discharge is generated within the discharge pixel cells 11 selected every sustaining pulse SUSP while a voltage caused by a wall charge and charged particles formed in advance within the discharge pixel cells 11 generating the address discharge is added to the sustaining pulse SUSP applied to the Y electrode lines Y1 to Ym and the Z electrode lines Z1 to Zm. On the other hand, the discharge pixel cells 11 in which the address discharge is not generated, do not generate a discharge because an electric field able to cause the discharge is not applied to the corresponding discharge pixel cells 11 even when the sustaining pulse SUSP is applied. If a plasma display occurs as described above, then a vacuum ultraviolet ray is generated. This vacuum ultraviolet ray excites the fluorescent layer 5 to display a picture.
As seen from FIG. 4 and FIG. 5, however, the conventional PDP has a problem in that, since the sustaining pulse SUSP applied to the adjacent sustaining electrode 10 is coupled between the adjacent discharge spaces 30, and have an inverted polarity with respect to each other, a mis-discharge may be generated between the adjacent discharge spaces 30. Also, it has a problem in that a time contributing to a luminescence in the entire sustaining interval is only about 1 xcexcs per sustaining pulse SUSP. More specifically, the sustaining pulse SUSP has a frequency of tens of kHz to hundreds of kHz and a pulse width of several xcexcs, but charged particles and wall charges generated while a discharge is caused by the sustaining pulse SUSP, reduce an electric field in the discharge space. As a result, because a discharge is not generated successively in a time interval when the sustaining pulse SUSP is applied, but a discharge is stopped just after the sustaining pulse SUSP was applied, the sustaining interval is not utilized effectively and the brightness is lowered.
Accordingly, it is an object of the present invention to provide a plasma display panel and driving apparatus and method thereof that are capable of improving the brightness.
Further object of the present invention is to provide a plasma display panel and driving apparatus and method thereof that are capable of preventing a mis-discharge.
In order to achieve these and other objects of the invention, according to one aspect of the present invention, each of a plurality of sustaining electrode groups in a PDP includes at least three electrodes a center electrode and two side electrodes, respectively spaced at different distances from the center electrode.
According to another aspect of the present invention, a PDP driving apparatus includes a sustaining electrode group including the at least three electrodes; and a sustaining electrode driver for applying the same polarity of voltage signals to side electrodes positioned at the outermost portions of each side of the center electrode.
According to still another aspect of the present invention, a PDP driving apparatus includes the steps of making a sustaining electrode group formed on a front substrate from at least three electrodes; and setting said at least three electrodes to have different spaces from each other to thereby generate at least two discharges continuously.